In the conventional operation of the power system, the demand and supply operation of electric power for maintaining the balance between demand and supply of electric power and the system operation for distributing electric power generated in power plants to consumers while ensuring power quality such as voltage are main operations.
As the demand and supply operation of electric power for maintaining the balance between demand and supply, demand and supply of electric power are controlled in an electric power company. The demand and supply control is to control the power generation amount to make equal to the load varied every moment and includes economic load distribution control for controlling long-period components longer than or equal to ten-odd minutes and frequency control for controlling short-period components of several minutes to dozens of minutes.
In the economic load distribution control of them, electric generators such as thermal, hydraulic and atomic electric generators installed in parallel with the power system are decided in consideration of power generation cost of the whole power system. A so-called economic operation for deciding the optimum output distribution of each power plant is subjected to the planned operation on the basis of a predetermined load curve during a day (daily load curve).
On the other hand, in the frequency control, imbalance between demand and supply of electric power is calculated from detection values of frequency and linkage line current and adjustment instructions for electric generators are supplied to each power plant on the basis of the calculated imbalance. In this case, the thermal and hydraulic electric generators are subjected to the frequency control but the atomic electric generators which have large output are frequently operated at fixed load. With regard to this point, in future, there is a tendency to reduce the thermal electric generators which emit greenhouse gases and increase the atomic power plants in view of the global environment problem. Accordingly, it is supposed that thermal power which is easy to adjust the output is reduced to thereby make adjustment between demand and supply of electric power difficult.
Next, as the system operation, the obligation that electric power in transformer substations and power transmission facilities is controlled to ensure the quality of electric power and the electric power is distributed to consumers is assumed. However, recently, there is a tendency to increase load due to the increased introduction amount of scattered-type power sources and the spread of electrification of all appliances. As a result, it is supposed that the load amount exceeds the capacity of the transformer substations and the pole transformers and in the present circumstances it is obliged to increase investment in plant and equipment in order to ensure the reliability of supply.
As a method of solving the above two problems, recently, attention is paid to secondary batteries containing storage batteries. The storage batteries are frequently installed on the consumer side and can store electric power. The storage batteries are mainly installed for the purpose of the following two objects in many cases.
The first object is to utilize the storage batteries as subsidiary use for rationalization of power cost on the consumer side and the second object is to control the current at the linkage point where micro-grids of the small-scale power system and the power system are linked
Here, the reason of utilizing the storage batteries as subsidiary use for rationalization of power cost on the consumer side which is the first object is described. When a consumer decides a power contract with the power company, the consumer predicts the maximum annual power consumption and makes the contract so as not to exceed the maximum annual power consumption in many cases. The reason is that the consumer must pay a penalty to the power company for exceeding the maximum annual power consumption.
Accordingly, when the consumer is provided with the storage batteries, the consumer can avoid exceeding the maximum annual power amount as well as reduce the contracted power itself. Further, the consumer can sell surplus power and accordingly it is profitable for the consumer. However, in the present circumstances, it is not profitable economically to sell the electric power stored in the storage batteries to the power system as it is and accordingly the storage batteries are used in combination with scattered-type power sources in order to improve the operation efficiency of the scattered-type power sources, so that electric power generated by the scattered-type power sources is sold in many cases.
Next, in the utilization method of the storage batteries as the micro-grids of the small-scale power system which is the second object, the storage batteries are installed in order to reduce the load on the power system by controlling the scattered-type power sources containing new energy and the load so as to make the current at the linkage point with the power system equal to 0 or fixed.
However, in order to control the storage batteries, it is necessary to monitor individual storage batteries and implement a complicated control procedure, which results in a higher construction cost of the control system. Accordingly, it is further necessary to permanently station a manager who operates the control system. As described above, when the storage batteries are introduced generally, the performance of the storage batteries is not fully utilized and surplus power is left, so that further utilizable potential is preserved.
As described above, since the storage batteries installed on the consumer side do not fully utilize the charge and discharge capacity of the storage batteries, the storage batteries can be further utilized. Patent Literature 1 describes the method of filling the potential of the secondary batteries containing the storage batteries.
Concretely, the method uses an apparatus in which the secondary batteries installed on the consumer side using electric power and which is connected to the power system which supplies electric power to the consumers and makes charge and discharge of electric power for the consumers are employed to control the power system. Here, the apparatus includes a control amount calculation part for calculating the total amount of charge and discharge of electric power by all secondary batteries necessary for control of the power system, an effect calculation part for calculating the sensitivity to the power system of the secondary batteries as control effect to the power system of the secondary batteries and a distribution amount calculation part which performs distribution calculation for distributing the total amount of charge and discharge of electric power calculated by the control amount calculation part to the secondary batteries in order of the control effect calculated by the effect calculation part, and the secondary batteries are controlled on the basis of the result of distribution calculation by the distribution amount calculation part.